Part of macOS
sharingdAirDrop and sharing
○ Leave it
Runs AirDrop, Handoff and other sharing between devices.
What it is
Looks after AirDrop, Handoff, and the Share menu’s nearby devices.
If you stop it
macOS starts it again straight away. Leave it.
The verdict
○ Leave it. Part of macOS, or something that starts again by itself. You never need to close these.
In Activity Monitor
sharingd
From Procession’s guide, in the words the app shows.